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  Degradable thiol-ene polymersRelated Patent Categories: Plant Protecting And Regulating Compositions, Plant Growth Regulating Compositions (e.g., Herbicides, Etc.), Designated Nonactive Ingredient Containing, Microencapsulating Or Encapsulating AgentDegradable thiol-ene polymers description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080070786, Degradable thiol-ene polymers. Brief Patent Description - Full Patent Description - Patent Application Claims
REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10/269,916, filed Oct. 10, 2002, which claims priority under 35 U.S.C. .sctn.119(e) from U.S. Provisional Application Ser. No. 60/328,669 filed Oct. 10, 2001, the complete disclosures of these priority documents are incorporated herein by reference. FIELD OF THE INVENTION [0003] The invention is directed to the production of degradable thiol-ene based polymers via photopolymerization. BACKGROUND OF THE INVENTION [0004] Recent approaches in the field of tissue engineering involve the use of polymeric biomaterials as cell scaffolds, which provide cells with a three-dimensional support material on which to grow. Despite a recent expansion in the design and development of suitable scaffold materials, there is still a lack of suitable scaffold materials with systematically variable properties. Without suitable materials available with a wide range of properties to serve as scaffolds for tissue engineering, it is unlikely that the field will achieve its full potential. [0005] Advances in polymer chemistry and materials science have spawned the development of numerous biomaterials and scaffolding methods that have potential uses in a wide range of tissue engineering applications. Several criteria must be achieved in the design of a biomaterial. First, the material must be biocompatible. That is, it must not promote an immune, allergenic, or inflammatory response in the body. Also, a method must exist to reproducibly process the material into a three-dimensional structure. Adhesive properties of the surface of the biomaterial must permit cell adhesion and promote growth. In addition, the biomaterial should have a high porosity to facilitate cell-polymer interactions, improve transport properties, and provide sufficient space for extracellular matrix generation. Finally, depending upon the particular application, the biomaterial should be biodegradable with an adjustable degradation rate so that the rate of tissue regeneration and the rate of scaffold degradation can be matched. [0006] Natural materials, such as collagen and many polysaccharides, generally exhibit a limited range of physical properties, are difficult to isolate, and cannot be manufactured with a high degree of reproducibility. However, natural materials often are more biocompatible and may even have specific biologic activity. Synthetic materials, on the other hand, can be cheaply and reproducibly processed into a variety of structures and the mechanical strength, hydrophilicity, and degradation rates of synthetic scaffolds are more readily tailored. However, synthetic polymers can cause inflammatory responses when implanted in the host. Recent tissue engineering endeavors have attempted to combine properties of both natural and synthetic polymers in the design of a suitable scaffold. [0007] Polylactide (PLA), polyglycolide (PGA) and their copolymers (PLGA) are polyesters based on naturally occurring lactic and glycolic acids (cc-hydroxy acids). They have been used as biodegradable sutures and implantable materials for more than two decades. They are biocompatible and biodegradable, and these polymers have a history of use as polymer scaffolds in tissue engineering. However, their highly crystalline and hydrophobic nature makes it difficult to control their biodegradation process and mechanical properties. Moreover, because of the lack of pendant functional groups, it is extremely difficult to modify the surface chemistry of PLA and PGA. For example, proteins and other molecules that may facilitate cell adhesion and growth cannot be easily attached to the backbone of these polymers because there is no chemical "handle" with which to derivatize these substrates. Attempts to introduce functional groups into these types of polymers include copolymerization of the lactide and glycolide cyclic monomers with more easily derivatizable monomers such as cyclic lysine monomers modified by peptide attachments. [0008] Recently, alternating copolymers of .alpha.-hydroxy acids and .alpha.-amino acids (polydepsipeptides) have been obtained with functional side groups. Additionally, poly(L-lactides) containing .beta.-alkyl .alpha.-malate units have been prepared by ring opening copolymerization of L-lactide with a cyclic diester. Major drawbacks remain with these lactide based copolymers including the difficulty in synthesis of cyclic monomers that are used in the copolymerization with lactide and the generally low reaction yields. Thus, the difficult synthesis and the low reaction yields make the commercialization of the modified polylactide biomaterials improbable and make it nearly impossible to tailor chemical, physical, and degradation properties of the final polymer. [0009] Photopolymerization systems have numerous advantages for matrix production. First, photoinitiation allows facile control over the polymerization process with both spatial and temporal control. For example, a liquid macromer solution can be injected into an area of the body, formed into a particular shape, and photopolymerized on demand using a light source. The final polymer hydrogel maintains the shape of that specific area of the body, allowing intimate control over the final shape of the hydrogel and improved adhesion and integration. In addition, the photocrosslinking chemistry creates covalently crosslinked networks that are dimensionally stable. [0010] Known photopolymerization processes, however, suffer from a number of drawbacks, including: the use of a separate initiator specie that is cytotoxic at relatively low concentrations, the difficulty in polymerizing thick samples because of light attenuation by the initiator, the inhibition of the radical polymerization by oxygen present in the air (which slows the polymerization), and the ability to fabricate gels with a diverse range of properties, especially gels with a high water content while maintaining high mechanical strength. Thus, there exists a need for biocompatible hydrogels which can polymerize in the absence of cytotoxic initiators and which can be tailored to have specific chemical, physical, and degradation properties under physiological conditions. SUMMARY OF THE INVENTION [0011] One embodiment of the present invention is a polymeric material having repeating units of the formula: --[--S--R.sub.1--S--C--C--R.sub.2--C--C--]--, wherein R.sub.1 and R.sub.2 are independent linkers, and at least one of R.sub.1 and R.sub.2 are degradable. R.sub.1 and R.sub.2 can be independently selected from poly(lactic acid), poly(ethylene glycol), poly(vinyl alcohol), and mixtures thereof, and one or both of R.sub.1 and R.sub.2 can have a degree of branching of greater than two. The polymeric material is preferably biocompatible, and can have a minimum dimension of at least about 4 cm. [0012] The polymeric materials of the present invention can be produced by a process that includes combining a first reactant of the formula R.sub.1--(C.dbd.C).sub.n with a second reactant of the formula R.sub.2--(SHF).sub.m, wherein n and m are independently integers greater than one and R.sub.1 and R.sub.2 are as described above. The combined reactants are then irradiated with light to cause reaction between the first and second reactants and eventually between the formed products to obtain the polymeric material. This process can include irradiating the reactants in the absence of a chemical initiator. [0013] In a further embodiment, the polymeric material can include at least one biologically active component encapsulated within it. The biologically active component can be selected from the group consisting of cells, tissues, and tissue aggregates, such as chondrocytes, immortalized cell lines, stem cells, honnone-producing cells, or fibroblasts. Additionally, the biologically active component can include pharmacologically active agents or agricultural chemicals. Pharmacologically active agent functional molecules can include analgesics, antipyretics, nonsteriodal antiinflammatory drugs, antiallergics, antibacterial drugs, antianaemia drugs, cytotoxic drugs, antihypertensive drugs, dermatological drugs, psychotherapeutic drugs, vitamins, minerals, anorexiants, dietetics, antiadiposity drugs, carbohydrate metabolism drugs, protein metabolism drugs, thyroid drugs, antithyroid drugs, or coenzymes. Agricultural chemical functional molecules can include fungicides, herbicides, fertilizers, pesticides, carbohydrates, nucleic acids, organic molecules, or inorganic biologically active molecules. [0014] In another embodiment, the polymeric material can be derivatized with a fanctional molecule, for example, by forming the polymeric material with excess thiol groups and reacting the functional molecule with such excess thiol groups. The functional molecules can be, for example, proteins, agricultural chemicals, or pharmacologically active agents. Protein functional molecules can include adhesion peptides, growth factors, hormones, antihormones, signaling compounds, serum proteins, albumins, macroglobulins, globulins, agglutinins, lectins, antibodies, antigens, enzymes, or extracellular matrix proteins. The polymeric material of the present invention can also be configured to form a degradable commodity plastic. [0015] A further embodiment of the present invention includes a thiol-ene hydrogel having poly(lactic acid), poly(ethylene glycol), and poly(vinyl alcohol) polymeric segments, wherein at least one of the segments has a degree of branching of greater than two. In this embodiment, the thiol-ene hydrogel has a modification selected from encapsulation of at least one biologically active component within the thiol-ene hydrogel and derivatization of the thiol-ene hydrogel with a functional molecule. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 shows the general scheme for thiol-ene polymerization. [0017] FIG. 2 shows a scheme for the formation of a thiol-ene hydrogel formed from derivatized PLA, PEG and PVA monomers. [0018] FIG. 3 shows schemes for derivatizations of poly(vinyl alcohol). [0019] FIG. 4 shows schemes for derivatizations of poly(lactic acid). DETAILED DESCRIPTION OF THE INVENTION Continue reading about Degradable thiol-ene polymers... Full patent description for Degradable thiol-ene polymers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Degradable thiol-ene polymers patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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